1. Field of the Invention
The present invention relates to a gas sensing material for sensing a local gas leaked or ejected from an inspection object. The present invention also relates to a gas inspecting method which uses the gas sensing material, is easy to carry out and is capable of carrying out sensing rapidly with high accuracy.
2. Description of the Related Art
Recently, hydrogen gas is attracting more and more attention. One reason for that is an energy problem, therefore, use of the hydrogen gas which is environmentally clean is taken into account in various fields. Examples of the application of the hydrogen gas include an electric vehicle having a fuel cell as its energy source, and a hydrogen vehicle with hydrogen fuel stored in a hydrogen storage alloy tank, and the like. Moreover, the following hydrogen energy society is expected: an energy obtained by any of a hydraulic power generation, a wind power generation, a photovoltaic power generation, an atomic power generation and the like is once converted into a hydrogen in a hydrogen manufacturing plant, then the hydrogen is stored in a hydrogen storage tank, for energy distribution to various applications of social life such as family fuel, traffic-and-transportation fuel and the like.
Another problem is structural material's brittleness caused by hydrogen. Recently, it has been obvious that the structural material becomes brittle and deteriorated due to water content in the environment or hydrogen caused by the water content. Clarifying the hydrogen's function which is deemed to be the main cause of the above structural material's brittleness may lead to solution of a long-year problem (environmental brittleness) in the field of material technology, giving a strong assistance to material problems indispensable for social infrastructure arrangement-maintenance and various big projects. Moreover, clarifying the hydrogen's function is expected to bring about a pervasive effect on the environmental countermeasure and a new technology in the field of electronics. However, the hydrogen in the structural material has an ultrafine amount of ppm digit and is likely to be mobile, therefore it is difficult to catch reality of the hydrogen. Moreover, a method of observing microscopic feature of destruction is not established. With the above, clarification of the environmental brittleness and its drastic countermeasure guideline are not making so much a progress as expected.
In terms of the above two social changes, development of a new sensing unit for sensing the hydrogen gas is required, especially, observation of microscopic hydrogen state involved by the structural material's brittleness caused by hydrogen, specifying hydrogen leak part in a hydrogen bomb, and an inspecting-analyzing method of carrying out the above easily, rapidly, highly accurately and quantitatively.
In the above state, Hydrogen MicroPrint Technique (hereinafter referred to as “HMPT method” as the case may be) which is a visualization technology of the hydrogen state in the structural material is attracting attention (for example, refer to “The Japan Institute of Metals, Vol. 62, No. 9, (1998), pp. 790-795” and “Light metal, No. 49, second issue (1999), pp. 89-96” and the like). The above “HMPT method” is a method of analyzing mobile behavior of the hydrogen, by using a direct reducing operation of an atomic hydrogen reaching the surface the structural material from inside of the structural material.
FIG. 1A shows a principle of the above hydrogen microprint technique (HMPT method), in which a photographic emulsion film 5 is so applied as to coat a surface of a hydrogen bomb 10 which is an inspection object. In the above state, when the atomic hydrogen in the hydrogen bomb 10 is leaked or ejected to the surface of the hydrogen bomb 10 for some reasons, a silver bromide (AgBr) 1 (which is present in a place to which the hydrogen is ejected) in the photographic emulsion layer 5 may be reduced to a silver atom (Ag) 3, as expressed by the following reaction formula 1 (refer to FIG. 1B). The above reduction of the silver bromide (AgBr) 1 to the silver atom (Ag) 3 is attributable to a strong reducing operation of the atomic hydrogen. Then, carrying out development and fixing treatment of the photographic emulsion film 5 in combination with the inspection object 10 may grow the thus caused silver atom (Ag) 3 to a silver particle (Ag) 3′ which can be observed by a microscope. On the other hand, an unreacted silver bromide (AgBr) 1 may be dissolved in a fixing liquid in the fixing, thereby, finally, the silver particle (Ag) 3′ alone may remain on the surface of the inspection object (refer to FIG. 1C). The hydrogen's mobile behavior can be checked by observing, with an optical microscope and an SEM (scanning electronic microscope), the thus remaining silver particle (Ag) 3′.AgBr+H→Ag+HBr  <Reaction formula 1>
The above HMPT method is epochal for its capability of sensing the local leak and local ejection of the hydrogen gas of the structural material, which sensing was conventional difficult. However, the HMPT method using the photographic emulsion may require an expert skill for operation in a dark room. Moreover, the HMPT method in need of developing treatment of the photographic emulsion may require equipment (development to fixing) and complicated operations. Moreover, in the HMPT method, the photographic emulsion film cannot be applied to the inspection object with high accuracy and the operation is complicated, therefore light-preventing property to the photographic emulsion is insufficient, failing to obtain sufficient accuracy.
Summarizing the above, the development of the gas inspecting method and the gas sensing material for the method is strongly demanded, which method enables an easy operation in a bright room and is capable of sensing rapidly and with high accuracy the local gas leaked or ejected from the inspection object.